PCB connector system is key to versatile interfacing

A key element of the company’s offering is the fact that all its test fixtures and interfaces are designed and manufactured in-house, which represents an increasing challenge because of the growing demand for lower-cost test solutions from customers. To accommodate this requirement, Peak needed a robust, computer-controlled interface board containing relay controls and digital IOs which could be configured flexibly to accept different customers’ test scenarios.

As such boards are not available in the marketplace at a reasonable cost, Peak took on the challenge of producing the board in-house.

The system had to be compact, low cost, expandable, robust, reliable and cover a wide voltage range, while at the same time incorporating multiple control interfaces, with one interface controlling a range of expansion modules. It also had to be compatible with multiple software drivers and all the components used in its construction had to be fully traceable.

The solution arrived at by Peak engineers was based around a master interface PCB which acts as the key interface between the controlling PC and all the expansion modules. It is fitted with three interfaces: USB, Ethernet and RS232. The board can be used as a stand-alone controller, or it can be 'piggy-backed' onto any expansion module or alternatively connected to expansion modules using a ribbon cable for maximum flexibility. The PCB assembly has a high speed I²C interface, 23 channels of digital I/O and 256kb of on-board memory, all controlled by any one of the three control interfaces. The PCB has a wide voltage input range from 7 to 36VDC, and measures only 100x50mm.

The on-board memory allows storage of data such as test cycles and date of manufacture, while the digital I/O is useful for monitoring sensor inputs and switching indicators and additional relays. The I²C interface is used for all expansion module communications, but can also be used as a stand-alone interface.

A 16-channel high-power SPDT relay board is used as the expansion module. This contains 16 SPDT 12A, 250VAC relays for general power switching. The relays can be switched and the status can be read back by the master interface PCB. All relays have LED indication and the PCB has the same wide voltage input range as the master interface board (7-36VDC) and measures 100x220mm. The relay board can be used for general switching inside test fixtures and systems, as well as in many other applications.

HARTING har-flex connectors were selected for board connectivity due to their small size, robustness and flexibility. They can be used as board-to-board connectors, allowing the master interface PCB to be connected to any expansion module directly; alternatively, the same connector can have a ribbon cable connected to connect subsequent expansion modules.

The small size of the connector allowed Peak to increase the pin count, allowing power lines to be commoned up and all communications and power to be passed down a single ribbon cable. As a result, expansion modules could be added in a matter of seconds.

HARTING’s har-flex family is a general-purpose PCB connector series based on a 1.27mm grid with SMT termination technology. With its straight, angled and cable variants, har-flex provides connectivity solutions for many different board-to-board and cable-to-board applications.

The different stacking heights of the mezzanine connectors and the flexible IDC connector cable lengths offer a high degree of freedom to the system design. A broad choice of configurations between six and 100 contacts in even-numbered positions is available.